Prosecutors in Italy are investigating allegations of systematic tax evasion among senior officials in the country’s top two divisions, in a probe that has reportedly targeted the heads of Napoli, Lazio, and Milan, among others.

No officials have been charged with wrongdoing but the Naples prosecutor Vincenzo Piscitelli said that authorities had seized €12m (£9m) in cash, property and other assets as part of their investigation into the tax dealings of 58 unnamed individuals in Italian football.

Financial police also conducted searches in the homes of more than two dozen players and agents, the news agency Ansa reported. The investigation has been dubbed “Fuorigioco”, or “offside”.

While prosecutors did not name any specific individuals being targeted in the inquiry, Italian media outlets said that the Napoli chairman Aurelio De Laurentiis, Adriano Galliani, the chief executive ofMilan, Claudio Lotito, the president of Lazio, and a handful of former players, had been involved in the investigation which was initiated in 2012.

At the centre of the investigation are allegations that players and other individuals doctored documents to try to avoid tax payments. The seizure of assets was a response to a “deep-rooted system” to evade taxes involving 35 football clubs and 100 individuals, Piscitelli said.

Investigators are alleging that players created false invoices for their clubs, which then got an illicit tax break by paying a lower amount of tax than was due. Several clubs did not return requests for comment by the Guardian, including Napoli and Lazio.

Milan confirmed in a statement posted on the club website that Galliani had been informed of an investigation into events that are “absolutely marginal and not founded and which will come to a resolution, in terms of both tax and criminal law, with a due dismissal”.

The allegations were also denied by De Laurentiis, who told the broadcaster Mediaset that the allegations were “nonsense”.

“I’m super-calm,” he said.”This is an old investigation from many years ago, it can’t be commented on and it concerns several clubs, not Napoli… Not having seen the documents, I can’t comment on the other clubs, but with regard to Napoli, I repeat: it’s nothing.”

It is not the first time prosecutors in Naples have dug into the tax affairs of some of Italy’s football giants. In 2013 dozens of clubs were searched as part of a tax fraud investigation that may be related to the one revealed on Tuesday.

A statement by prosecutors at the time indicated that foreign clubs were also being examined and that the investigation involved the avoidance of payments in connection to player transfers.